Contact lenses have been used commercially to improve vision since the 1950s. The first contact lenses were made of hard materials. Although these lenses are still currently used, they are not suitable for all patients due to their poor initial comfort and their relatively low permeability to oxygen. Later developments in the field gave rise to soft contact lenses, based upon hydrogels, which are extremely popular today. Many users find soft lenses are more comfortable, and increased comfort levels can allow soft contact lens users to wear their lenses longer than users of hard contact lenses.
It is desirable to manufacture silicone-containing contact lens using reduced or no diluent systems, which can enable the cured polymer to be “dry released” from the mold parts, placed directly into the final package containing packing solution for equilibration. Typically, the zero diluent systems containing high levels of PVP tend to produce cured lenses that are very brittle. These lenses when released using mechanical force are susceptible to physical damage. Applicants have found the incorporation of at least one mono-ether terminated, mono-methacrylate terminated polyethylene glycol significantly lowers the level of brittleness in the cured lenses. Thus, the cured lenses are less liable to fracture when subjected to stress during the lens release process. The at least one mono-ether terminated, mono-methacrylate terminated polyethylene glycol also allows for tuning the visco-elastic properties of the cured polymers for desirable mechanical lens release without the use of liquids.